As you can plainly see, a yo-yo is superior weapon in many respects. It has reach. It can be used to disarm and trip. One can perform a variety of amusing tricks with it. (See the Yo-Yo Man in action here.) With all that in mind, here’re stats for the martial yo-yo:

Martial Yo-Yo

The martial yo-yo is a light exotic melee weapon. The martial yo-yo consists of an axle that connects to two beveled metal disks. A length of martial twine loops around the axle. A martial yo-yo is wielded by holding the free end of the martial twine and allowing the force of a throw to spin the connected disks. This causes the martial twine to unwind, allowing the martial yo-yo’s spin to wind itself back to the wielder’s hand.

Yo-Yo Fighter (Ex): At 1st level, a yo-yo magus gains Exotic Weapon Proficiency (martial yo-yo) as a bonus feat. He gains a competence bonus to attack rolls with a martial yo-yo. The competence bonus equals +1 for levels 1st-4th; +2 for 5th-8th; +3 for 9th-12th; +4 for 13th-16th; and +5 for levels 17th and higher.

The yo-yo magus is otherwise proficient with only simple weapons.

Yo-Yo Acrobatics (Ex): At 1st level, as part of a move action either before or after making an attack with a martial yo-yo, a yo-yo magus can make an Acrobatics check with a bonus equal to his magus level.

This feature replaces the ability to cast cantrips. The magus can learn and prepare detect magic and read magic as 1st-level spells.

Yo-Yo Mystic (Su): At 7th level, when a yo-yo magus prepares his magus spells, he can decide to expend 1 or more points from his arcane pool, up to his Intelligence bonus. For each point he expends, he can treat any one spell prepared as if it were affected by one of the following metamagic feats: Disruptive Spell, Elemental Spell, Flaring Spell, Lingering Spell, Rime Spell, or Toppling Spell. In order to gain the effects of the metamagic feat, the yo-yo magus must cast the affected spell via spell combat or spellstrike while wielding a martial yo-yo. The metamagic effect does not adjust the level of the prepared spell.